Use of acrylic graft polymers in the field of collagen-based substrates, and the substrates, skins and leathers thus obtained

ABSTRACT

The invention concerns the technical sector of collagen-based substrates, notably hides, leathers, undressed hides and reconstituted leathers, and more specifically the use of acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives, together with the smoothing agents consisting of the said grafted acrylic polymers. The invention also concerns collagen-based substrates, notably hides, leathers, undressed hides and reconstituted leathers smoothed using these said grafted acrylic polymers. The invention also concerns leather objects smoothed using these said grafted acrylic polymers.

The present invention concerns the technical sector of collagen-based substrates and notably hides, leathers, undressed hides and reconstituted leathers, and more specifically the use of acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives in the aim of allowing smoothing of the said substrate without the use of crosslinking agents, notably formol.

The invention also concerns smoothing agents consisting of the said acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives.

The invention also concerns collagen-based substrates, notably hides, leathers, undressed hides and reconstituted leathers smoothed using these said grafted acrylic polymers.

The invention also concerns leather objects smoothed using these said grafted acrylic polymers.

Currently the finishing of hides, leathers, undressed hides and reconstituted leathers intended for the end consumer requires a treatment of these substrates by a process consisting essentially of five stages.

The first is a stage of sorting of the passes or hides or again substrates, which is undertaken in the abattoirs and/or in the tanneries, as desired by the client.

It will be noted that to facilitate reading of the present description, the Applicant has chosen to use the word hide to designate all types of collagen-based substrates, including notably hides, leathers, undressed hides and reconstituted leathers.

Thus the term hide will be understood to include all the substrates mentioned above.

Concerning the widely used hide finishing process, the second stage, still called river work, constitutes a stage in the preparation of the sorted hide, which is still, at this stage, putrescible.

This stage comprises firstly the soaking or dressing of the hide to clean the said hide, followed by the unhairing and liming of this cleaned hide to create points for mounting of the hide, which points will enable the various hide treatment additives to be fixed subsequently.

When this liming has been accomplished, the hide can be subjected to a skiving action followed by a shaving action corresponding to the removal of the subcutaneous part, which has no purpose, followed by actions of bating and finally of drenching, which is an enzymatic reaction to clean the keratin remains and the interfibrillary spaces.

When these various handling operations which constitute the stage known as river work have been accomplished the hide is subjected to a third stage of treatment, a stage which is broken down firstly into pickling, i.e. acid conditioning of the hide to allow the penetration of tannins into the hide, and subsequently the tanning itself to make the hide rot-proof.

This tanning of the hide habitually makes use of mineral derivatives such as, notably, chromium-, aluminium- or zirconium-based salts, together with organic derivatives such as hydrolysable vegetal tannins such as, for example, glucosides of the chestnut tree, Vallonnee, vinegar plant or Myrobolam types, or of organic derivatives such as condensed vegetal tannins, including among others catechic oligomers of the Quebrach, mimosa or gambir type.

These organic derivatives can also be synthetic tannins which can replace the vegetal tannins. They are then called substitution tannins.

These substitution tannins are compounds rich in OH⁻ in their structure and are mainly formol phenolic or naphtol-phenol condensates.

These synthetic organic derivatives can also be secondary tannins used as a supplement to other tannins. They have less tanning power, but have other properties, notably including dispersing, filling or “full” properties, or lightening or other properties.

These secondary tannins are also sulfonic naphthalene condensates, sulfonic aromatic acid, urea-formol, or again precondensed melamine and other condensates, but are also other than synthetic tannins such as, notably, aldehydes of the formol type, glyoxal, glutaraldehyde, aldehyde derivatives mainly multi-function products such as aldehyde-alcohols, phosphoniums, fatty chain sulfochlorides and other sulfochlorate paraffins.

When the third stage of the treatment is completed and the hide has become rot-proof, the fourth stage of the process is undertaken, consisting in all the operations undertaken after tanning, which is called currying.

This currying includes the wet operations such as curing, which consists in allowing the hides to stay stacked for 24 hours to perfect the tanning, neutralisation, retanning, dyeing, nourishing agents to soften the hide, and mechanical operations such as draining, drying, tempering or re-wetting, staking, which consists in stretching the hide to soften it at a degree of humidity of around 23% to 28%, framing, which consists in stretching the staked hides on to frames to flatten them, and sliding these frames into a drying machine to eliminate the previous moisture, trimming, which is a manual operation consisting of eliminating the frayed edges of the hide which make the skin unpresentable, and smoothing.

This mechanical smoothing operation consists in smoothing the hide using a metal, glass or agate cylinder, or cylinder of any other material, or again using a plate or any other method for shining the hide.

This operation is accompanied by a heating which encourages the shine to “rise”, since it is undertaken on a dry hide during currying, after trimming and framing, or again after the fifth stage of the process, which is the finishing of the hide on conclusion of manufacture.

Currently, for this smoothing operation, the skilled man in the art must generally use casein to give the skin shine, and must spray a casein crosslinking agent, notably formol, to fix the casein and attain the friction resistance specifications required by the end user.

This operation using casein following by a spraying of a casein crosslinking agent, notably formol, arises to the skilled man in the art problems of handling and environmental problems.

The specifications sheet generally applied requires that the formol contents in the hides have:

-   -   a content of less than or equal to 400 ppm for industrial         leathers,     -   a content of less than or equal to 300 ppm for leathers intended         for clothing,     -   a content of less than or equal to 40 ppm for leathers intended         for baby clothing.

Secondly, the handling problems are constituted by the need to use casein and then to spray, during a second stage, the crosslinking agent of the said casein.

Completely unexpectedly, the Applicant has found that the use, on collagen-based substrates, and notably hides, leathers, undressed hides and reconstituted leathers, of acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives enables the abovementioned problems posed to arisen to the skilled man in the art to be resolved; i.e. allows firstly problems relating to manipulation due to the use of casein followed by a spraying of crosslinking agent to be avoided, secondly allows all or part of the casein crosslinking agent, notably formol, to be eliminated, and thirdly enables the smoothing operation before the finishing operation, giving by this means the advantage of obtaining the smoothed appearance, which will enhance the finishing operation.

In addition to responding to the increasingly strict toxicity requirements and to the specifications of friction resistance required by the end user, this elimination of the use of substantial quantities of crosslinking agent, notably formol, together with the elimination of this double stage of spraying enables the collagen substrate and more particularly the hide or leather to be given properties of fullness, fineness of grain and increased shine. These properties of increased shine thus result in the natural appearance of the collagen substrate being preserved, and more particularly of the hide or of the leather.

To resolve these problems, the skilled man in the art has no prior art which might offer them any solution. The skilled man in the art is, indeed, familiar with the German patent DE 44 16 877 which teaches use of grafted polymers by proteins to resolve the problems of the lightening of colours, or of resistance to light and to heat.

The skilled man in the art familiar with patent GB 2 137 654, which teaches use of these grafted polymers to garnish the flanks of the hide and to fill hides tanned with chromium.

Another patent (U.S. Pat. No. 4,631,063) describes the use of grafted polymers as a dyeing aid to give the hide stronger colour.

None of these techniques known until today enable the skilled man in the art is to free themselves from the operations to use casein and to spray a crosslinking agent.

These aims are attained as claimed in the invention thanks to the use as a smoothing agent, on collagen-based substrates and notably hides, leathers, undressed hides and reconstituted leathers, of acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives.

This use is characterised in that the said grafted acrylic polymers are acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives.

This use is, preferably, characterised in that it is used at a rate of 0.8% to 6% by dry weight, relative to the so-called “wet blue” support weight, and more particularly at a rate of 1.2% to 2.4% by dry weight, relative to the so-called “wet blue” support weight, of the said acrylic polymers grafted with one or more proteinic derivatives or of the natural or synthetic fatty derivatives.

The weight of the so-called “wet blue” support is the weight of the hide after the river work, chromium tanning, wringing and skiving operations.

More particularly, these grafted acrylic polymers, according to the invention as a smoothing agent, result from various radical polymerisation processes in the presence of the proteinic derivatives or of the natural or synthetic fatty derivatives for grafting.

Even more particularly, use as a smoothing agent of these polymers resulting from homopolymerisation or radical copolymerisation of unsaturated ethylene monomers in the presence of a proteinic derivative or derivatives, or from the natural or synthetic fatty derivative or derivatives for grafting is characterised in that the said agent is a product of radical polymerisation of at least one of the monomers from among: acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic anhydride and/or 2-acrylamido-2-methyl-1-propane sulfonic acid, 2-methacrylamido-2-methyl-1-propane sulfonic acid, 3-methacrylamido-2-hydroxy-1-propane sulfonic acid, allylsulfonic acid, methallylsulfonic acid, allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, 2-hydroxy-3-(2-propenyloxy) propane sulfonic acid, 2-methyl-2-propene-1-sulfonic acid, ethylene sulfonic acid, propene sulfonic acid, 2-methyl sulfonic acid, styrene sulfonic acid and/or its salts, vinyl sulfonic acid, sodium methallylsulfonate, sulfopropyl acrylate or methacrylate, sulfomethylacrylamide, sulfomethylmethacrylamide, or again from acrylamide, methylacrylamide, esters of acrylic or methacrylic acids such as, notably, ethyl acrylate, butyl acrylate, methyl methacrylate, acrylate phosphate or ethylene methacrylate or glycol propylene, or from vinylpyrrolidone, vinylcaprolactam, isobutylene, diisobutylene, vinyl acetate, styrene, alphamethylstyrene, vinylmethylether, allylics such as, notably, allylamine and its derivatives, preferentially chosen from acrylic acid or methacrylic acid in the presence of one or more of the proteinic derivatives or of the natural or synthetic fatty derivatives chosen from neat's foot oil, sheep's foot oil, whale oil, synthetic spermaceti oil, seal oil, tallow, suint grease, olein, stearin, suintin, lanolin, lecithin, phosphatidic acids, cephaline, cholesterols, phytosterols, casein, eel oils, herring oils, shark oil, sardine oil, fish oil, egg yolk, insect wax, for example of bees, carnauba wax, candellila, ricin oil, olive oil, copra, palm kernel oil, groundnut oil, cotton oil, colza oil, almond oil, avocado oil, tung oil, borage oil, cocoa oil, camelia oil, cameline oil, campher oil, carthame oil, chaulmoogra oil, hempseed oil, croton oil, wheat seed oil, corn seed oil, jojoba oil, karite oil, linseed oil, maize oil, marmot oil, menhaden oil, rapeseed oil, hazelnut oil, walnut oil, apricot core oil, poppy oil, oiticica oil, ongokea oil, palm oil, pecan oil, grape pip oil, perilla oil, pine nut oil, pistachio nut oil, acetylated ricin oil, rice oil, sesame oil, soya oil, tortoise oil, sunflower oil, liquid paraffin, mink oil, abietic acids and their salts, naphtalene sulfonic acids and their salts, formol melamines, glutaric, glutamic, aspartic, butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, arachidic, behenic, lignoceric, cerotic, elaidic, petroselinic, lauroleic, myristoleic, palmitoleic, oleic, gadoleic, erucic, linoleic, linolenic, eleostearic, licanic, parinaric, arachidonic, clupanodonic or taririric acids, or again isanic acids, preferably chosen from among casein, lecithin or linseed oil.

In a particular manner also, use as a smoothing agent of these polymers is characterised in that the acrylic or methacrylic acid esters are chosen from alkyloxypolyalkylene glycol acrylate or methacrylate and particularly is methoxypolyethylene glycol methacrylate.

These polymers resulting particularly from homopolymerisation or from radical copolymerisation of the monomers previously listed in the presence of the proteinic derivative or derivatives or from the natural or synthetic fatty derivatives, or from their mixtures mentioned above, are characterised even more particularly in that the mass rate of proteinic derivatives or of natural or synthetic fatty derivatives, relative to the total quantity of monomers, is between 2.5% and 40%, and preferably between 5% and 10%.

These polymers can be obtained by radical polymerisation or copolymerisation of the abovementioned monomers in the acid state, partially neutralised or totally neutralised, and preferably in the acid state in a polymerisation medium which can be water, one of the alcohols or a water-alcohol mixture, or again one of the solvents chosen from methanol, ethanol, propanol, isopropanol, the butanols, or mixtures of them, or again dimethylformamide, dimethylsulfoxide, tetrahydrofuran, acetone, methylethylketone, ethyl acetate, butyl acetate, hexane, heptane, benzene, toluene, xylene, halogenated solvents such as carbon tetrachloride, chloroform, methylene chloride, or again the glycol monopropylene ethers, or mixtures of them and their analogues.

However, the skilled man in the art will adapt the pH of the polymerisation medium according to the proteinic derivative or derivatives, or of the natural or synthetic fatty derivative or derivatives, or according to the mixtures of thereof used in this polymerisation reaction.

These neutralisation agents are chosen either from the group constituted by the compounds containing alkaline cations, particularly sodium and potassium, or again lithium, ammonium, or indeed the primary or secondary aliphatic and/or cyclic amines such as, for example, the ethanolamines, mono- and diethylamine, or again cyclohexylamine, or from the group constituted by the compounds containing alkaline-earth divalent cations, particularly magnesium and calcium, or again zinc, or the group constituted by the compounds containing trivalent cations, in particular aluminium, or again by certain compounds containing cations of higher valences, or are a mixture of at least two of the abovementioned agents.

In another variant, the homopolymer or copolymer produced from the polymerisation reaction in the presence of the proteinic derivative or derivatives or of the natural or synthetic fatty derivative or derivatives may be treated and separated into several phases, according to static or dynamic processes known to the skilled man in the art, by one or more polar solvents belonging notably to the group constituted by water, methanol, ethanol, propanol, isopropanol, the butanols, acetone, tetrahydrofuran, or mixtures of thereof. One of the phases then corresponds to the polymer used according to the invention as a smoothing agent.

The invention also concerns smoothing agents consisting of the said acrylic polymers grafted with the said proteinic derivatives or natural or synthetic fatty derivatives.

Thus, the smoothing agents according to the invention are characterised in that they are products of radical polymerisation of at least one of the monomers from among: acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic anhydride and/or 2-acrylamido-2-methyl-1-propane sulfonic acid in acid or partially neutralised form, 2-methacrylamido-2-methyl-1-propane sulfonic acid in acid or partially neutralised form, 3-methacrylamido-2-hydroxy-1-propane sulfonic acid in acid or partially neutralised form, allylsulfonic acid, methallylsulfonic acid, allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, 2-hydroxy-3-(2-propenyloxy) propane sulfonic acid, 2-methyl-2-propene-1-sulfonic acid, ethylene sulfonic acid, propene sulfonic acid, 2-methyl sulfonic acid, styrene sulfonic acid and/or its salts, vinyl sulfonic acid, sodium methallylsulfonate, sulfopropyl acrylate or methacrylate, sulfomethylacrylamide, sulfomethylmethacrylamide, or again from acrylamide, methylacrylamide, esters of acrylic or methacrylic acids such as, notably, ethyl acrylate, butyl acrylate, methyl methacrylate, acrylate phosphate or ethylene methacrylate or glycol propylene, or from vinylpyrrolidone, vinylcaprolactam, isobutylene, diisobutylene, vinyl acetate, styrene, alphamethylstyrene, vinylmethylether, allylics such as, notably, allylamine and its derivatives, preferentially chosen from acrylic acid or methacrylic acid in the presence of one or more of the proteinic derivatives or of the natural or synthetic fatty derivatives chosen from neat's foot oil, sheep's foot oil, whale oil, synthetic spermaceti oil, seal oil, tallow, suint grease, olein, stearin, suintin, lanolin, lecithin, phosphatidic acids, cephaline, cholesterols, phytosterols, casein, eel oils, herring oils, shark oil, sardine oil, fish oil, egg yolk, insect wax, for example of bees, carnauba wax, candellila, ricin oil, olive oil, copra, palm kernel oil, groundnut oil, cotton oil, colza oil, almond oil, avocado oil, tung oil, borage oil, cocoa oil, camelia oil, cameline oil, campher oil, carthame oil, chaulmoogra oil, hempseed oil, croton oil, wheat seed oil, corn seed oil, jojoba oil, karite oil, linseed oil, maize oil, marmot oil, menhaden oil, rapeseed oil, hazelnut oil, walnut oil, apricot core oil, poppy oil, oiticica oil, ongokea oil, palm oil, pecan oil, grape pip oil, perilla oil, pine nut oil, pistachio nut oil, acetylated ricin oil, rice oil, sesame oil, soya oil, tortoise oil, sunflower oil, liquid paraffin, mink oil, abietic acids and their salts, naphtalene sulfonic acids and their salts, formol melamines, glutaric, glutamic, aspartic, butyric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, arachidic, behenic, lignoceric, cerotic, elaidic, petroselinic, lauroleic, myristoleic, palmitoleic, oleic, gadoleic, erucic, linoleic, linolenic, eleostearic, licanic, parinaric, arachidonic, clupanodonic or taririric acids, or again isanic acids, preferably chosen from among casein, lecithin and linseed oil.

In a particular manner also, the smoothing agent according to the invention is characterised in that the acrylic or methacrylic acid esters are chosen from alkyloxypolyalkylene glycol acrylate or methacrylate and particularly is methoxypolyethylene glycol methacrylate.

More particularly, the smoothing agents according to the invention are characterised in that the mass rate of the proteinic derivatives or of the natural or synthetic fatty derivatives or of mixtures of thereof, relative to the total quantity of the monomers, is between 2.5% and 40%, preferably between 5% and 10%.

The smoothing agent according to the invention, obtained by radical polymerisation or copolymerisation of the abovementioned monomers, is in the acid state, or in the partially neutralised state, or the totally neutralised state, and is preferably in the acid state, i.e. a pH of under 7.

The neutralisation agents are chosen from among those previously described. In another variant, the smoothing agent according to the invention produced from the polymerisation reaction in the presence of the proteinic derivative or derivatives or from the natural or synthetic fatty derivative or derivatives may, as previously described, be treated and separated into several phases.

The invention also concerns collagen substrates smoothed using the said acrylic polymers grafted with the said proteinic derivative or derivatives or natural or synthetic fatty derivatives.

These hides, with the general meaning described above, according to the invention, are characterised in that they contain the said acrylic polymers grafted with the said proteinic derivatives or natural or synthetic fatty derivatives or mixtures of thereof, and are characterised more particularly in that they contain 0.8% to 6% by dry weight, relative to the weight of the so-called “wet blue” support, and particularly 1.2% to 2.4% by dry weight relative to the weight of the so-called “wet blue” support, of the said acrylic polymers grafted with proteinic derivatives or natural or synthetic fatty derivatives.

The invention also concerns leather objects smoothed using the said acrylic polymers grafted with the said proteinic derivative or derivatives, or natural or synthetic fatty derivatives.

The invention will be better understood on reading the description of the non-limitative examples below.

EXAMPLE 1

The aim of this example is to highlight is also the shining properties obtained through the use of acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives according to the invention.

In this aim, for each of the tests in the example, a goat's hide is prepared called “wet blue” after the river works, chromium tanning, wringing and skiving operations. The “wet blue” hide is then weighed, and this weight is the reference weight for the stages of neutralisation, retanning, dyeing and nourishment which follow.

All these stages are undertaken in identical way for all tests.

To accomplish this, the “wet blue” hide is introduced in a cleaning drum at 40° C. containing a cleaning bath consisting of 150% by weight of water relative to the weight of the “wet blue” hide and of 1% by weight, relative to the weight of the “wet blue” hide, of the cleaning agent Actol DB sold by the company ATC. This bath containing the hide is stirred for 20 minutes at a speed of between 10 and 12 revolutions per minute, before being emptied from the drum.

The stage of neutralisation at 35° C. is then undertaken up to a pH of 4.5, by addition, into the drum, of the neutralising medium, consisting of 100% by weight of water relative to the weight of the “wet blue” hide, and 1% by weight, relative to the weight of the “wet blue” hide, of the neutralising agent Actan NH sold by the company ATC.

After 30 minutes of stirring at a speed of between 10 and 12 revolutions per minute, the neutralising bath is, in its turn, emptied from the drum to allow room for the retanning stage. To accomplish drum, to this drum containing the hide, 50% by weight of water is added relative to the weight of the “wet blue” hide and 3% by weight, relative to the weight of the “wet blue” hide, of a black colouring agent sold by the company ATC under the name Dyacor Black ANT, and it is then stirred 3 times 10 minutes, at a speed of between 10 and 12 revolutions per minute, before adding 50% by weight of water, relative to the weight of the “wet blue” hide, and 1.5% by weight, relative to the weight of the “wet blue” hide, of a nourishment for hide sold by the company ATC under the name Actoil NM.

After this addition, the whole mixture is stirred for 20 minutes, still at a speed of 10 to 12 revolutions per minute, before adding 3% by weight, relative to the weight of the “wet blue” hide, of a synthetic tannin sold by the company ATC under the name Actan PO.

After this addition, the whole mixture is stirred for 20 minutes at the same speed, before adding 10% by weight, relative to the weight of the “wet blue” hide, of a vegetal mimosa tannin sold by the company Seta under the name Seta Sun. The whole mixture is also stirred for one hour at the same speed before adding 1% by weight, relative to the weight of the “wet blue” hide, of formic acid.

After adding formic acid and stirring for 20 minutes at a speed of between 10 and 12 revolutions per minute, the bath is emptied and then rinsed.

The retanning operation then continues for all tests by adding at 50° C. of 50% by weight of water, relative to the weight of the “wet blue” hide, and of 0.1% by weight, relative to the weight of the “wet blue” hide, of a biocide sold by the company ATC under the name Biocide C3, and then by stirring the mixture for 5 minutes at a speed of between 10 and 12 revolutions per minute.

It is then continued by adding at 50° C. of 50% by weight of water, relative to the weight of the “wet blue” hide, and of 0.5% by weight, relative to the weight of the “wet blue” hide, of a neutralising agent sold by the company ATC under the name Actan NH.

The whole mixture is then stirred for 10 minutes at the same speed before adding 1% by weight, relative to the weight of the “wet blue” hide, of a nourishment for hide sold by the company ATC under the name Actoil VI, 2.5% by weight, relative to the weight of the “wet blue” hide, of another nourishment for hide sold by the company ATC under the name Actoil SGC, and finally before adding 0.5% by weight, relative to the weight of the “wet blue” hide, of a final nourishment for hide sold by the company ATC under the name Actoil NLP.

Once these three previously described stages of cleaning, neutralisation and then retanning have been undertaken, the various tests of the example then implement the various polymers to be tested as a smoothing agent through the addition into the drum of the various agents for testing under stirring at 10 to 12 rpm for 30 minutes. When these agents have been implemented, a final addition of 1% of formic acid by weight relative to the weight of the “wet blue” hide is made.

This having been done, for each of the tests, smoothing is undertaken using a smoothing machine fitted with a glass cylinder. A measurement of the shine of the smoothed hide is then undertaken by simple application, to the smoothed hide, of a shine meter of the “micro Tri gloss” type manufactured by BYK-GARDNER GmbH.

Test No. 1

This test is a control test which implements 1.2% by dry weight, relative to the weight of the “Wet blue” hide, of an acrylic acid homopolymer.

The value of the shine obtained is equal to 4.1.

Test No. 2

This test illustrates the invention and implements 1.2% by dry weight, relative to the weight of the “Wet blue” hide, of a casein-grafted acrylic acid polymer in a weight ratio of equal to 92.5% acrylic acid and 7.5% casein.

The value of the shine obtained is equal to 4.8.

If the sample of hide used in this test is subjected to a subsequent polishing stage, the value of shine, measured under the same conditions, is equal to 24.1.

Test No. 3

This test illustrates the invention and implements 4.5% by dry weight, relative to the weight of the “Wet blue” hide, of a casein-grafted acrylic acid polymer in a weight ratio of equal to 97.5% acrylic acid and 2.5% casein.

The value of the shine obtained is equal to 5.3.

Test No. 4

This test illustrates the invention and implements 0.8% by dry weight, relative to the weight of the “Wet blue” hide, of a casein-grafted acrylic acid polymer in a weight ratio of equal to 80% acrylic acid and 20% casein.

The value of the shine obtained is equal to 4.7.

Test No. 5

This test illustrates the invention and implements 1.2% by dry weight, relative to the weight of the “Wet blue” hide, of a casein-grafted acrylic acid polymer in a weight ratio of equal to 95% acrylic acid and 5% casein.

The value of the shine obtained is equal to 5.2.

Test No. 6

This test illustrates the invention and implements 1.2% by dry weight, relative to the weight of the “Wet blue” hide, of a casein-grafted acrylic acid polymer in a weight ratio of equal to 90% acrylic acid and 10% casein.

The value of the shine obtained is equal to 8.1.

Test No. 7

This test illustrates the invention and implements 0.9% by dry weight, relative to the weight of the “Wet blue” hide, of a linseed oil-grafted acrylic acid polymer in a weight ratio of equal to 90% acrylic acid and 10% linseed oil.

The value of the shine obtained is equal to 5.9.

Test No. 8

This test illustrates the invention and implements 1.8% by dry weight, relative to the weight of the “Wet blue” hide, of a linseed oil-grafted acrylic acid polymer in a weight ratio of equal to 90% acrylic acid and 10% linseed oil.

The value of the shine obtained is equal to 6.3.

Test No. 9

This test illustrates the invention and implements 1.8% by dry weight, relative to the weight of the “Wet blue” hide, of a casein-grafted acrylic acid polymer in a weight ratio of equal to 90% acrylic acid and 10% casein.

The value of the shine obtained is equal to 5.9.

Test No. 10

This test illustrates the invention and implements 1.8% by dry weight, relative to the weight of the “Wet blue” hide, of a polymer of acrylic acid and methacrylic acid grafted with lecithin, in a weight ratio of equal to 45% acrylic acid, 45% methacrylic acid and 10% lecithin.

The value of the shine obtained is equal to 5.5.

Test No. 11

This test illustrates the invention and implements 1.8% by dry weight, relative to the weight of the “Wet blue” hide, of a linseed oil-grafted acrylic acid polymer in a weight ratio of equal to 60% acrylic acid and 40% linseed oil.

The value of the shine obtained is equal to 4.9.

Test No. 12

This test illustrates the invention and implements 2.3% by dry weight, relative to the weight of the “wet blue” hide, of a copolymer, of pH 5, of acrylic acid grafted with olein in a weight ratio of equal to 75.6% acrylic acid, 14.4% maleic anhydride and 10% olein.

The value of the shine obtained is equal to 7.9.

Test No. 13

This test illustrates the invention and implements 2.3% by dry weight, relative to the weight of the “wet blue” hide, of a copolymer, of pH 5, of acrylic acid grafted with casein in a weight ratio of equal to 85.5% acrylic acid, 9.5% 2-acrylamido-2-methyl-1-propane sulfonic acid and 5% casein.

The value of the shine obtained is equal to 8.6.

Test No. 14

This test illustrates the invention and implements 2.3% by dry weight, relative to the weight of the “wet blue” hide, of a copolymer, of pH 5, of acrylic acid grafted with linseed oil in a weight ratio of equal to 68% acrylic acid, 15.3% acrylamide, 1.7% sodium methallylsulfonate and 15% linseed oil.

The value of the shine obtained is equal to 5.6.

Test No. 15

This test illustrates the invention and implements 2.3% by dry weight, relative to the weight of the “wet blue” hide, of a copolymer, of pH 5, of acrylic acid grafted with lanolin in a weight ratio of equal to 73.6% acrylic acid, 13.8% methacrylic acid, 4.6% methacrylamide and 8% lanolin.

The value of the shine obtained is equal to 6.1.

Test No. 16

This test illustrates the invention and implements 2.3% by dry weight, relative to the weight of the “wet blue” hide, of a copolymer, of pH 6.5, of methacrylic acid grafted with ricin oil in a weight ratio of equal to 81% methacrylic acid, 4.5% butyl acrylamide, 4.5% styrene and 10% ricin oil.

The value of the shine obtained is equal to 10.1.

Test No. 17

This test illustrates the invention and implements 2.3% by dry weight, relative to the weight of the “wet blue” hide, of a polymer, of pH 5, of acrylic acid grafted with fish oil in a weight ratio of equal to 80% of acrylic acid and 20% fish oil.

The value of the shine obtained is equal to 5.9.

Test No. 18

This test illustrates the invention and implements 2.3% by dry weight, relative to the weight of the “wet blue” hide, of a copolymer, of pH 5, of acrylic acid grafted with copra oil in a weight ratio of equal to 76% acrylic acid, 4.75% ethylene glycol methacrylate phosphate, 14.25% methoxypolyehthylene glycol methacrylate of molecular weight 750 and 5% copra oil.

The value of the shine obtained is equal to 8.7.

Test No. 19

This test illustrates the invention and implements 2.3% by dry weight, relative to the weight of the “wet blue” hide, of a copolymer, of pH 5, of acrylic acid grafted with neat's foot oil in a weight ratio of equal to 85.5% acrylic acid, 4.5% vinyl acetate and 10% neat's foot oil.

The value of the shine obtained is equal to 8.1.

Test No. 20

This test illustrates the invention and implements 1.8% by dry weight, relative to the weight of the “wet blue” hide, of a polymer, of pH 5, of acrylic acid grafted with casein and linseed oil in a weight ratio of equal to 90% of acrylic acid, 5% casein and 5% linseed oil.

The value of the shine obtained is equal to 6.0.

Test No. 21

This test illustrates the invention and implements 0.9% by dry weight, relative to the weight of the “wet blue” hide, of a polymer, of pH 5, of acrylic acid grafted with lecithin in a weight ratio of 90% acrylic acid and 10% lecithin and 0.9% by dry weight, relative to the weight of the “wet blue” hide, of a polymer, of pH 5, of acrylic acid grafted with lanolin in a weight ratio of equal to 90% acrylic acid and 10% lanolin.

The value of the shine obtained is equal to 5.9.

Reading all these results shows that the use of acrylic polymers grafted with proteinic derivatives or natural or synthetic fatty derivatives according to the invention enables increased shine properties to be obtained on the exclusively smoothed hide, and enables the smoothing operation to be undertaken before the finishing operation.

This shine value enables the natural appearance of the hide to be preserved. 

1. A method of treating collagen based substrates comprising: applying acrylic polymer grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives to collagen based substrates.
 2. A method as claimed in claim 1, wherein said acrylic polymer grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives is a product of radical polymerisation of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic anhydride, 2-acrylamido-2-methyl-1-propane sulfonic acid, 2-methacrylamido-2-methyl-1-propane sulfonic acid, 3-methacrylamido-2-hydroxy-1-propane sulfonic acid, allylsulfonic acid, methallylsulfonic acid, allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, 2-hydroxy-3-(2-propenyloxy) propane sulfonic acid, 2-methyl-2-propene-1-sulfonic acid, ethylene sulfonic acid, propene sulfonic acid, 2-methyl sulfonic acid, styrene sulfonic acid, salts of styrene sulfonic acid, vinyl sulfonic acid, sodium methallylsulfonate, sulfopropyl acrylate, sulfopropyl methacrylate, sulfomethylacrylamide, sulfomethylmethacrylamide, acrylamide, methylacrylamide, esters of acrylic acid, esters of methacrylic acid, glycol propylene, vinylpyrrolidone, vinylcaprolactam, isobutylene, diisobutylene, vinyl acetate, styrene, alphamethylstyrene, vinylmethylether, and allylics in the presence of one or more of the proteinic derivatives or of the natural or synthetic fatty derivatives selected from the group consisting of neat's foot oil, sheep's foot oil, whale oil, synthetic spermaceti oil, seal oil, tallow, suint grease, olein, stearin, suintin, lanolin, lecithin, phosphatidic acids, cephaline, cholesterols, phytosterols, casein, eel oils, herring oils, shark oil, sardine oil, fish oil, egg yolk, insect wax, carnauba wax, candellila, ricin oil, olive oil, copra, palm kernel oil, groundnut oil, cotton oil, colza oil, almond oil, avocado oil, tung oil, borage oil, cocoa oil, camelia oil, cameline oil, campher oil, carthame oil, chaulmoogra oil, hempseed oil, croton oil, wheat seed oil, corn seed oil, jojoba oil, karite oil, linseed oil, maize oil, marmot oil, menhaden oil, rapeseed oil, hazelnut oil, walnut oil, apricot core oil, poppy oil, oiticica oil, ongokea oil, palm oil, pecan oil, grape pip oil, perilla oil, pine nut oil, pistachio nut oil, acetylated ricin oil, rice oil, sesame oil, soya oil, tortoise oil, sunflower oil, liquid paraffin, mink oil, abietic acid salts of abietic acid, naphthalene sulfonic acid, salts of naphthalene sulfonic acid, formol melamines, glutaric acid, glutamic acid, aspartic acid, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, elaidic acid, petroselinic acid, lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, linoleic acid, linolenic acid, eleostearic acid, licanic acid, parinaric acid, arachidonic acid, clupanodonic acid, taririric acid, and isanic acid.
 3. The method according to claim 2, wherein said at least one monomer is selected from the group consisting of esters of acrylic acid and esters of methacrylic acid, wherein said esters of acrylic acid is alkyloxypolyalkylene glycol acrylate and said esters of methacrylic acid is alkyloxypolyalkylene glycol methacrylate.
 4. The method according to claim 2, wherein between 2.5% and 40%, by mass, of the proteinic derivatives or of natural or synthetic derivatives, is present relative to the total quantity of the monomer.
 5. The method according to claim 1, wherein 0.8% to 6% by dry weight of acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives, relative to the weight of the “wet blue” support, is applied.
 6. A smoothing agent wherein said smoothing agent comprises acrylic polymers grafted with one or more proteinic derivatives or natural or synthetic fatty derivatives.
 7. The smoothing agent according to the claim 6, wherein said smoothing agent is produced by the radical polymerisation of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic anhydride, 2-acrylamido-2-methyl-1-propane sulfonic acid, 2-methacrylamido-2-methyl-1-propane sulfonic acid, 3-methacrylamido-2-hydroxy-1-propane sulfonic acid, allylsulfonic acid, methallylsulfonic acid, allyloxybenzene sulfonic acid, methallyloxybenzene sulfonic acid, 2-hydroxy-3-(2-propenyloxy) propane sulfonic acid, 2-methyl-2-propene-1-sulfonic acid, ethylene sulfonic acid, propene sulfonic acid, 2-methyl sulfonic acid, styrene sulfonic acid, salts of styrene sulfonic acid, vinyl sulfonic acid, sodium methallylsulfonate, sulfopropyl acrylate, sulfopropyl methacrylate, sulfomethylacrylamide, sulfomethylmethacrylamide, acrylamide, methylacrylamide, esters of acrylic acid, esters of methacrylic acid, glycol propylene, vinylpyrrolidone, vinylcaprolactam, isobutylene, diisobutylene, vinyl acetate, styrene, alphamethylstyrene, vinylmethylether, and allylics in the presence of one or more of the proteinic derivatives or of the natural or synthetic fatty derivatives selected from the group consisting of neat's foot oil, sheep's foot oil, whale oil, synthetic spermaceti oil, seal oil, tallow, suint grease, olein, stearin, suintin, lanolin, lecithin, phosphatidic acids, cephaline, cholesterols, phytosterols, casein, eel oils, herring oils, shark oil, sardine oil, fish oil, egg yolk, insect wax, carnauba wax, candellila, ricin oil, olive oil, copra, palm kernel oil, groundnut oil, cotton oil, colza oil, almond oil, avocado oil, tung oil, borage oil, cocoa oil, camelia oil, cameline oil, campher oil, carthame oil, chaulmoogra oil, hempseed oil, croton oil, wheat seed oil, corn seed oil, jojoba oil, karite oil, linseed oil, maize oil, marmot oil, menhaden oil, rapeseed oil, hazelnut oil, walnut oil, apricot core oil, poppy oil, oiticica oil, ongokea oil, palm oil, pecan oil, grape pip oil, perilla oil, pine nut oil, pistachio nut oil, acetylated ricin oil, rice oil, sesame oil, soya oil, tortoise oil, sunflower oil, liquid paraffin, mink oil, abietic acid, salts of abietic acid, naphthalene sulfonic acid, salts of naphthalene sulfonic acid, formol melamines, glutaric acid, glutamic acid, aspartic acid, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, elaidic acid, petroselinic acid, lauroleic acid, myristoleic acid, palmitoleic acid, oleic acid, gadoleic acid, erucic acid, linoleic acid, linolenic acid, eleostearic acid, licanic acid, parinaric acid, arachidonic acid, clupanodonic acid, taririric acid, and isanic acid.
 8. The smoothing agent according to claim 7, wherein said at least one monomer is selected from the group consisting of esters of acrylic acid and esters of methacrylic acid, wherein said esters of acrylic acid is alkyloxypolyalkylene glycol acrylate and said esters of methacrylic acid is alkyloxypolyalkylene glycol methacrylate.
 9. The smoothing agent according to claim 7, wherein said smoothing agent comprises between 2.5% and 40% by mass the proteinic derivatives or of the natural or synthetic fatty derivatives, relative to the total quantity of the monomers.
 10. A collagen-based substrate comprising the smoothing agent as claimed in claim
 6. 11. The collagen-based susbstrate according to claim 10 wherein said substrate comprises 0.8% to 6% by dry weight of the smoothing agent, relative to the support of the “wet blue” support.
 12. A leather article comprising the smoothing agent as claimed in claim
 6. 